Engine code 0420
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CF Beginner
Joined: Aug 2018
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Engine code 0420
I have a 2011 equinox have been getting 0420 code . Changed O2 sensor twice also previously changed cat. Can’t seem to shake this problem. Had trimming chain problem last year after changing cat and changed engines also. This year still having some problems. Any suggestions?
CF Pro Member
Joined: Sep 2010
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Are you sure you installed the correct catcon? If you installed a Federal Emissions cat on a vehicle that came with California (or other state that's lower than Federal) Emissions, that's why the P0420 code persists.
Also, which brand of oxygen sensor did you install? I don't trust Boach, which is what most auto parts chains stock. I recommend AC Delco, NTK, Denso or Delphi.
Also, which brand of oxygen sensor did you install? I don't trust Boach, which is what most auto parts chains stock. I recommend AC Delco, NTK, Denso or Delphi.
CF Pro Member
Joined: Sep 2010
Posts: 981
Likes: 83
You need to look at the option sticker located on the glove box door & visible when you open it and look for:
NT7 (Tier 2 Federal Emissions)
NU5 (California Emissions)
NU6 (PZEV California Emissions)
This will confirm which emissions standard your Equinox was made to comply with. Even though Louisiana obviously doesn't need to comply with California's emissions standards, your ECM is still programmed to comply with them. This is common with fleet vehicles. As far as I can tell after briefly researching this, all 2010+ Equinox comply with California standards.
Lastly, there are two cat cons on the Equinox. The downstream oxygen sensor is between them. The second cat doesn't affect the code (P0420) because it is not monitored with another oxygen sensor.